Paul, I was told by a Wiltshire Council Councillor, when I asked why the national limit was being reduced to 50mph in many places, and in others to 40.
He said it was because the road surfaces were no longer fit to go any faster and there was no money to repair them. Reducing the limit would, it was believed, reduce claims on the Council for wheel damage.
He also said that the Police no longer had any say in the application of speed limits on rural roads, which means that most are unenforceable.
What a world... because of "Free" Third Party Claim lawyers we have to put up with stupid limits.